Presently, it is common for mobile operators to have national mobile communication networks, such as networks for mobile data and/or voice communication, for example GSM, GPRS, 3G, LTE, etc. When a mobile communication unit is brought outside of the coverage area of a certain network and into the coverage area of the network of another operator, conventional roaming gives rise to problems with high and unpredictable costs for data and/or voice communication.
These problems are especially common when it comes to mobile data traffic, where costs during roaming with variable tariffs can amount to more than 1000 times higher per data unit as compared to mobile data traffic in the home network. Many times there are no efficient ways of keeping track of the costs during a stay abroad or the like. As a consequence, a user risks unpleasant surprises regarding mobile data costs when returning from a stay within the coverage area of the network of a foreign operator.
EP2144458 describes a method using an interface means to provide a SIM card with information regarding available networks for data traffic as well as connection costs for said networks.
WO2007132233 describes a method for remotely configuring a mobile communications device, and for registering and authenticating users of such a device. Configuration data is received and converted by the device, and a configuration database is updated using the data. In one example, different Subscriber Identity Module (SIM) cards with different International Mobile Subscriber Identities (IMSI) can be tied to the same user account for roaming.
WO2005081962 describes a method for keeping costs down for voice communication when roaming, by establishing a corresponding Voice over IP (VoIP) call when requesting a voice call from a mobile unit over a cellular network.
WO2008103446 describes a method in which the IMSI of a SIM is associated with a local telephone number (MSISDN) when roaming, in order to enjoy local tariffs.
WO2001076188 describes a method in which a care of address is used with a mobile device when performing IP-based communication.
The international patent application PCT/SE2011/050886, which has not been published on the filing date of the present application, describes a method according to which a local IMSI is automatically distributed to a SIM card in a mobile device roaming into a visited country.
A drawback of this method is that it exposes the home operator to the risk of misconfiguration in partner networks. Such misconfiguration will lead to malfunction of the roaming function. Namely, the method relies upon that a location update request message from a roaming device is correctly routed from the local roaming partner, via a local PSTN operator and a home PSTN operator, to the home network. This in turn involves processing of the IMSI, for instance using a routine involving translating the IMSI into a so called Global Title number format, which can be understood correctly by the PSTN operators. In the case of a network with many roaming partners, different IMSI number ranges for different purposes, customer agreements and so forth, the risk for misconfiguration of the IMSI number conversion at one or several of the local roaming partners is non-negligible.